I'd either go for the Sigma 70-200mm 2.8 or the Tamron 70-300mm VC USD (great image stabilizer and very sharp).
The Sigma 70-200mm ist quite a bit more expensive than the other solutions but it's probably the best solution. I'd rather go for a 1.4x extender though.

Just a quick calculation:
To closely capture a player's body in motion let's assume you need a 1.6x2,4m frame on the court - which is 100x the size of your sensor (making calculations pretty easy). So if you're 20m away from the player you need a 20m/100 = 200mm focal length to get the shot.
A tennis court is roughly 11x24m (36x78 feet) so if you're sitting close to the net a shooting distance of 20m might just be ok. If you're sitting further away or more to one side you may well need to cover a distance of 30m or even 40m. Which in turn would imply you'd need a 300mm or even 400mm to get a shot that tightly framed.
If you'd love to capture an upper body shot your target-frame shrinks to around half of the above (say 1.2x1.6m) which increases the focal length needed for that shot by another 50% (roughly). So you're now talking about a 300mm lens from 20m distance or a 600mm from 40m distance.
You can see that capturing sports even in "closed quarters" might need some pretty long lenses. Combine this with the need to shoot at fast shutter-speeds makes you (and me) wish to use a lens like the stabilized Sigma 120-300/2.8. Unfortunately the price of this baby is past 2000 (USD, GBP, EUR) So you might consider the non-stabilized Sigma 100-300/4.0 or a good 70-200 + 1.4x TC as an option. As always with Sigma lenses make sure you can give the lens back without prohibitive restocking fee should you get a decentered copy (see my sad story of the 100-300/4.0 here). But when you can get a good copy, the (non-stabilized) 100-300/4.0 was tested with pretty good results (see there).

update bought the Sigma 70-200mm 2.8 and the Tamron 70-300mm VC USD both great lenses didn't get the teleconverter but wish i had so now looking is their a converter that will work with both these lenses . I have read that the sigma and the teleplus sp300 are the same is this right any recommendation greatly appreciated

If you use the best quality for shooting, enlarging and cropping will still give a reasonable quality photo. Shooting a bit wide also lets cropping where you want it and not cut off any part of the players body when shooting since they move so fast.